Torque amplifier for dancer field rheostats



Sept. 10', 1940. C. w. DRAKE' 509 I 'ronqms AMPLIFIER FOR DANCER FIELDRHEOSTAI'S Filed April 25,,1939

1 5low Slay I I (fl INVENTOR Chester W Bra/re.

wnm-zssss: A/XM J BY W I M8 'ATTORNEY Patented. Sept. 10, 1940 roaounmpirma roa mmcna rmm ansos'rsrs Chester W. Drake, Irwin, Pa., asslgnorto 'Westingliouse Electrio & Manufacturing Company,

East Pittsburgh, Pa, sylvania a corporation of Penn- Application April25, 1939, Serial No. 270,037

12 Claim My invention relates to an operating mechanism for rheostats,and more specifically to a torque amplifier for a "dancer fieldrheostat.

In winding machines and the like wherein long thin sheets or materialsuch as paper, or long strips of material suchas threads or rubber arewound or conveyed, it"is often desirable to control the speed of travelof such material in accordance with the size of a loop of the material.

For example, a weighted body may rest on the loop and its verticalmovement as the result of changes in the loop size may be transmitted toa rheostat, which, in turn, controls the speed of a motor which iseffective to restore the loop to its initial optimum 1| size. It hasbeen found, however, in such applications that the amount of torquewhich can be developed by a weighted body resting on the loop and actingthrough a predetermined vertical distance is insufllcient to operatelarge rheostats.

It is, therefore, necessary that a force amplifying means or relay, orboth, be interposed between the weighted body and the rheostat in orderto develop suillcient torque to operate the large rheostat.

5 An object of my invention is to provide a novel torque amplifyingmeans on a "dancer type rheostat.

Another object of my invention is to provide relay means to a torqueamplified dancer rheostat which relay means includes a mercury switchwhich controls a motor which, in turn, drives a rheostat contact arm,thereby varying the speed olf a second or main motor in accordance withvariations in the size of the loop of the material being wound.

' Other objects and advantages will become more apparent from a study ofthe following specification when considered in conjunction with the ac-L companying drawing, in which the single figure is a diagrammatic viewembodying my invention andinwhich:

Numeral i denotes a strip of material, such as paper, rubber, or thelike, which is being wound in a winding machine or which is otherwisebeing transferred from one part of a machinetc another. The material isdriven by constant speed roll 2, then forming a loop 3, and finally isdriven by a variable speed roll 4, which roll 4 is driven by a variablespeed electric motor 5. Motor 5 is illustrated as being a shunt motorhaving a field winding 8 and a rheostat I.- In moving the contact arm 3of the rheostat I, the speed of the motor 6 may be controlled; in otherwords, if

5 contact arm '3 is moved to the left, thereby putting in moreresistance, the field. developed by winding 6 is weakened and the speedof motor 5 is increased; likewise when contact arm 3 is moved to theright the speed of motor-.5 is decreased. It "will be readily observedthat in order to keep the size of loop 3 substantially constant, thespeed of motor 5 should vary directly in accordance with the size ofsuch loop.

The torque amplifying means for the rheostat, in accordance with myinvention, comprises an arm 3 which is loosely pivoted on shaft [0,which shaft is journaled to a stationary bearing member (not shown).Pivoted at the opposite end of arm 3 is a link H which is secured to aweighted member l2 which rests on loop ,3. It will thus be obvious thatas the size of loop 3 varies,.link II will move vertically in accordancewith such variations and will, in turn, move arm 9 about shaft [0 asa'pivot in accordance with the size of the loop. Loosely pivoted on anintermediate portion of arm 9 is a gear l3 having a shaft portion It,Rigidly secured on gear 13 by a support I5 is a double pole mercuryswitch l6 having a pair of contact members H at the left end thereof anda similar pair of contact members l8 on the right end thereof. Integralwith shaft 10 are contact arm 8, a smaller gear is and a sprocket 20.Sprocket 20 is driven by a reversible motor 2! having two reversingwindings, 22 and 23. The motor drive is through shaft 24, sprocket 25,and chain26.

The operation of the device is as follows: Assume that the start pushbutton is depressed thereby closing contact members 21. A circuit willbe completed which may be traced from supply conductor 28 throughconductor 29, contact members 21, the bridged contact members 30 of thestop push button switch, relay coil 3|, then through a parallel path,one going through the armature of motor 5, the other going troughconductor 32, the resistors of rheostat I, contact arm 8, conductor 33,and field winding 6 then through a common conductor 34 to the othersupply conductor 35. Energization of relay coil 3| will effect closingof contact members 36 which shunts contact members 21 of the start pushbutton. Hence even though the start push button is released, therebyallowing its spring to open the contact members thereof, a parallelcircuit will, 50 nevertheless, be established through contact members33- and will be maintained as long as relay coil 3| remains energized.When the stop push button is depressed thereby opening contact members30, relay coil II will become deenergized thereby opening contactmembers 36 and interrupting the motor circuit. 7

If the size of loop 3 diminishes an abnormal amount, weighted member i2will be raised and through link II, will move arm 9. in a clockwisedirection about shaft l0 as an axis. Gear I9 will tend to remainstationary because of the inertia and friction of the parts in drivingengagement therewith including sprockets 20 and 25 and the reversiblemotor 21. Hence, gear I3 will rotate about stationary gear I9, at thesame time tilting the mercury switch [6 to the right until finally theright-hand contact members i8 are closed by the mercury, therebycompleting a circuit through one of the reversing windings 23 ofreversible motor 2!. The above circuit may be traced from supplyconductor 28 through conductors 31, 38, contact members i8, conductor39, field winding 23, the armature or" motor 2!, conductor 40 to theother supply conductor 35.

Motor 2| will thus rotate in such direction so as to rotate gear i9together with contact arm 8 in a clockwise direction. Clockwise rotationof contact arm 8 will cut out a portion of the resistance in therheostat 1, hence will effect slowing of the speed of motor 5 which inturn will drive roll 4 at a lower speed thereby allowing loop 3 toincrease in size. As hereinbefore explained, gear i9 is integral withcontact arm 8. Hence as contact it rotates in a clockwise direction,gear it also rotates in such direction and by its geared relation togear l3 it will rotate the gear it in a counter-clockwise direction.This rotation will continue until-switch i6 is tilted sufiiciently so asto open contact members it and interrupt the circuit through thereversible motor 2!. It will be observed that the amount of shorteningof loop 3 controls the amount of tilting of mercury switch 16 which, inturn, determines the length of time that the reversible motor 2| mustoperate before mercury switch it is restored to its original or neutralposition until both contact members I! and I8 are again open.

Likewise if loop 3 should for some reason become abnormally large, arm 9will be moved in a counter-clockwise direction thereby rotating ear i3in a counter-clockwise direction about the gear i 9 until contactmembers I! of the mercury switch are closed, thereby completing thecircuit through the other field winding 22 which will effect a drive ofgear I9 in a counter-clockwise direction thereby moving contact arm 8 tothe left to put more resistance in series with field winding 6 so as tospeed up motor 5 and roll 4, so as to again shorten the loop.Simultaneously, gear I3 will be rotated in a clockwise direction untilmercury switch I6 is tilted sufficiently to open contact members IT,thereby deenergizing reversible motor 2! and stopping the abovedescribed movement.

In view of the fragile characteristics of the material i, which may bethin paper, rubber, or the like, only a very small force may be appliedto link H by the changes in size of the loop; hence in order to applysufficient torque to contact arm 3, a relay controlled reversible motoris used. By making the diameter of gear [3 larger than that of gear l9so as to provide a larger number of teeth on gear l3 than on gear i9,say in the ratio of about 2 to 1 or even greater, it is possible .toachieve a greater angular movement of contact arm 8; hence a greaterchange in resistance in rheostat l for a given change in the size of theloop, thereby affording speed control through a wide range of speeds forthe motor 5. This large movement of the rheostat contact arm in responseto a small movement of arm 9 is the result of the change in loop and isquite important for the operation of most rheostats in order to obtainsufficient variation in resistance to secure the desired range of speedcontrol. In accordance with my invention, it is possible to securemovement of the rheostat contact arm almost to the extent of 360 inresponse to a relatively small change in loop size. Of course, if suchlarge movement of the rheostat arm is unnecessary, gears l3 and I8 maybe of substantially the same diameter or gear is may even be larger thangear 13.

Speed adjustment may also be had with my system of control. Forinstance, instead of obtaining control by a loop such as 3, arm 9 could,as well, be manually settable at any position along the are (shown indotted lines) so as to manually obtain preset speed control of motor 5.Instead of controlling the speed of motor 5 in order to restore loop 3to a predetermined optimum size, speed of motor 5 may be controlled forany other reason whatsoever. Furthermore, while a winding machine hasbeen described, it is obvious that sheets of rubber or the like whichare moved by conveyors may likewise have regulatable travelling speed.

While a shunt motor 5 has been described, any other variable speed motorcontrol system such as a variable voltage system may be substituted andmay be controllable by the movement of contact arm 8.

I am, of course, aware that others, particularly after having had thebenefit of the teachings of my invention, may devise other devices andsystems of control embodying my invention, and I, therefore, do not wishto be limited to the specific showings made in the drawing and thedescriptive disclosure hereinbetore made, but wish to be limited only bythe scope of the appended claims and such prior art that may bepertinent.

I claim as my invention:

1. Operating mechanism for an electrical switch comprising, incombination, an operating arm, a rotatable member pivoted on saidoperating arm, intermediate between the ends of the arm, an electricalswitch which is actuable by partial rotation of said rotatable memberabout said pivot, a second rotatable member also plyoted on saidoperating arm and which is of smaller diameter than said first rotatablemember and which is in driving engagement therewith, friction meansnormally restraining said second rotatable member against rotationthereby allowing rotation of said first rotatable member about saidsecond rotatable member as the result of operation of said operatingarm, thereby actuating said switch.

2. Operating mechanism for an electrical switch comprising, incombination, an operating arm, a gear pivoted on said operating armintermediate the ends thereof, a mercury switch rigidly mounted on saidgear, a second gear also pivoted on said operating arm and which is ofsmaller diameter than said first gear and which is geared thereto,friction means normally restraining said second gear against rotation sothat upon predetermined movement of said operating arm, said first gearwill rotate about said second gear to sufilciently tilt said mercuryswitch to effect actuation thereof.

3. Operating mechanism for an electrical switch comprising, incombination, an operating arm, a gear pivoted on said operating armintermediate the ends thereof, a double pole mercury switch rigidlymounted on said gear, a second gear also pivoted on said operating armand which is of smaller diameter than said first gear and which isgeared thereto, friction means normally restraining said second gearagainst rotation so that upon predetermined movement of said operatingarm in one direction, said first gear will rotate about said second gearsufilciently to tilt said mercury switch in one direction so as to closeone of the poles ,of the mercury switch, and upon predetermined movementof said operating arm in an opposite direction, said gear will rotateabout said second gear sunk ciently to tilt said mercury switch in anopposite direction so as to close the other of said poles, said secondgear being rotatable to an intermediate position for restoring saidmercury are ODBIL 4. Operating mechanism for an electricalswitchcomprising, in combination, an operating arm, a gear pivoted onsaid operating arm intermediate the ends thereof, a mercury switchrigidly mounted on said gear, a second gear also pivoted on saidoperating arm and which is of smallerdiameter than said first gear andwhich is geared thereto, friction means normally restraining said secondgear against rotation so that upon predetermined movement of saidoperating arm, said first gear will rotate about said second gear tosufiiciently tilt said mercury switch to effect actuation thereof, meansfor rotating said second gear in such direction so as to tilt saidmercury switch in an opposite direction so as to restore said mercuryswitch to its original position.

5. Inc. device for conveying long, thin, strips of material, means whichare -actuable by predetermined variations in the size of a loop of astrip of said material, operating mechanism 1 which is actuable by saidmeans and which comprises, in combination, an operating arm, a rotatablemember pivoted on said operating arm intermediate the ends of the arm,an electrical switch which is actuable by partial rotation of saidrotatable member about said pivot, a second rotatable member alsopivoted on said operating arm and which isof smaller diameter than saidfirst rotatable member and which is in driving engagement therewith,friction means normally restraining said second rotatable member againstrotation thereby allowing rotation of said first rotatable member aboutsaid second rotatable member as the result of operation of saidoperating arm, thereby actuating said switch.

6. In a device for conveying long, thin, strips of material, means whichare actuable by predetermined variations in the size of a loop of astrip of said material, operating mechanism which is actnable by saidmeans and which comprises, in combination, an operating arm, a gearpivoted on said operating arm intermediate the ends thereof, a mercuryswitch rigidly mounted,

on said gear, a second gear also pivoted on said operating arm and whichisof smaller diameter than said first gear and which is geared thereto,friction means normally restrainingsaid second gear against rotation sothat upon predetermined movement of said operating arm, said first gearwill rotate about said second gear to sufliciently tilt said mercuryswitch to eiiect actuation there of.

7. In a device for conveying long, thin, strips of material, means whichare actuable by predetermined variations in the size of a loop of astrip of said material, operating mechanism which is actuable by saidmeans and which comprises, in combination, an operating arm, a gearpivoted on said operating arm intermediate the ends thereof, a mercuryswitch rigidly mounted on said gear, a second gear also pivoted on saidoperating arm and which is of smaller diameter than said first gear andwhich is geared thereto, friction means normally restraining said secondgear against rotation so that upon predetermined movement of saidoperating arm, said first gear will rotate about said second gear tosufiiciently tilt said mercury switch to effect actuation thereof, meansfor rotating said second gear in such direction so as to tilt saidmercury switch in an opposite direction so as to restore said mercuryswitch to its original position.

8. In a device for conveying long, thin strips of material, meanssupported by a loop of said material and which is movable by an amountwhich is proportional to the size of said loop, operating mechanismwhich is operable by said means and which comprises an operating armwhich is connected to said means, a rotatable member-pivoted on saidoperating arm intermediate the ends of the arm, an electrical switchwhich is actuable by partial rotation of said rotatable member aboutsaid pivot, a second rotatable member also pivoted on said operating armand which is of smaller diameter than said first rotatable member andwhich is in driving engagement therewith, friction means normallyrestraining said second rotatable member against rotation therebyallowing rotation of said first rotatable member about said secondrotatable member as the result of operation ofsaid operating arm therebyactuating said switch.

9. In a device for conveying long, thin strips of material, meanssupported by a loop of said material and which is movable by an amountwhich is proportional to the size of said loop, operating mechanismwhich is operable by said means, and which comprises an operating armwhich is connected to said means, a gear pivoted on said operating armintermediate the ends thereof, a mercury switch rigidly mounted on saidgear, a second gear also pivoted on said operating arm and which is ofsmaller diameter than said first gear and which is geared thereto,friction means normally restraining said second gear against rotation sothat upon predeter mined movement of said operating arm, said firstgearwill rotate about said second gear to sufil ciently tilt saidmercury switch to effect actuation thereof.

10. In a device for conveying long, thin strips of material, meanssupported by a loop of said material and which is movable by an amountwhich is proportional to the size of said loop, operating mechanismwhich is operable by said means and which comprises an operating armconnected to said means, a gear pivoted on said operating armintermediate the ends thereof, a double pole mercury switch rigidlymounted on said gear, a second gear also pivoted on said operating armand which is of smaller diameter than said firstgear and which is gearedthereto,

said first gear will rotate about said second gear 15 sufiiciently totilt said mercury switch in one direction so as to close one of, thepoles of the mercury switch, and upon predetermined movement of saidoperating arm in an opposite direction, said gear will rotate about saidsecond gear sufficiently' to tilt said mercury switch in an oppositedirection so as to close the other of said poles, said second gear beingrotatable to an intermediate position wherein saidmercury is restored toa position in which both of its poles are open.

11. In a device for conveying long, thin strips of material, meanssupported by a loop of said material and which is movable by .an amountwhich is proportional to the size of said loop, operating mechanismwhich is operable by said means and which comprises an operating armwhich is connected to said means, a gear pivoted on said operating armintermediate the ends thereof, a mercury switch rigidly mounted on saidgear, a second gear which is also pivoted on said operating arm andwhich is geared to said first gear, motor means coupled to said secondgear and which, when inoperative, possesses suilicient inertia torestrain said second gear'against rotation thereby allowing a rotationof said first gear about said second gear as the result-oi operation ofsaid operating arm due to an abnormal change in the size of said loop,thereby actuating said mercury switch to efie'ct operation of saidmotor. 12. In a device for conveying long, thin strips of material,means supported by a loop of said material and which is movable by anamount which is proportional to the size of said loop, operatingmechanism which is operable by said means and which comprises anoperating arm which is connected to said means, a gear pivoted on saidoperating arm intermediate the ends thereof, a double pole mercuryswitch rigidly mounted on said gear, a second gear which is also pivotedon said operating arm and which is geared to said first gear, a motorfor efiecting travel of saidmaterial and a circuit therefor including avariable resistor having a contact arm'which is driven by said secondgear, reversible motor means coupled to said second gear and which, wheninoperative, possesses sufiicient inertia to restrain said second gearagainst rotation.thereby allowing rotation of said first gear about saidsecond gear as the'result ofoperation of said operating arm due to anabnormal change in the size of said loop, thereby closing one of saidpoles of said mercury switch to eflect rotation of said reversiblemotor-in one direction if the loop is too large, or closing the other ofsaid poles to effect rotation 01' said reversible motor in an oppositedirection if the loop is too small, either of said rotations of saidreversible motor restoring both poles of said mercury switch to the openposition and at the same time moving said contact arm to sufiicientlyvary the speed of said main motor so as to restore the size of said loopto its original

